Method of producing an SrTiO3 /YBa2 Cu3 O7 layer system and a layer system as thus produced as a high-temperature superconductor

Abstract

c-axis oriented YBa 2 Cu 3 O 7 layers are grown with intervening SrTiO 3 layers bridged over steps at which there is a transformation to a-axis crystal-oriented growth. The multilayer superconductor has YBa 2 Cu 3 O 7 layers which are not thicker than 500 nm while the intervening layers of SrTiO 3 have thicknesses of 20 to 30 nm.

We claim: 
     
       1. A method of producing a multilayer high temperature superconductor, comprising the steps of: (a) growing a c-axis crystal-oriented YBa 2  Cu 3  O 7  layer upon a substrate until formation of an a-axis crystal oriented region occurs;   (b) upon formation of said a-axis crystal oriented region and development of steps between a-axis crystal-oriented and c-axis crystal-oriented regions on a YBa 2  Cu 3  O 7  surface of said layer, and, after the growth of said c-axis crystal oriented YBa 2  Cu 3  O 7  layer to a thickness of at least 300 nm and not more than 500 nm, interrupting growth of the c-axis crystal-oriented YBa 2  Cu 3  O 7  layer;   (c) upon interruption in growth of the c-axis crystal-oriented YBa 2  Cu 3  O 7  layer in step (b), applying a SrTiO 3  layer in a thickness of at least 20 nm and at most about 30 nm to said surface until said steps between a-axis and c-axis regions are covered; and   (d) thereafter continuing the growth of said c-axis crystal-oriented YBa 2  Cu 3  O 7  layer upon the SrTiO 3  layer, thereby forming a stack of layers.   
     
     
       2. The method defined in claim 1 wherein steps (b) through (d) are repeated until said stack has a multiplicity of said layers formed therein. 
     
     
       3. The method defined in claim 1 wherein said stack is formed with a multiplicity of alternating SrTiO 3  layers and YBa 2  Cu 3  O 7  layers and each SrTiO 3  layer lying between two YBa 2  Cu 3  O 7  layers has a thickness of 20 to 30 nm. 
     
     
       4. A multilayer high temperature superconductor made according to claim 1, comprising a multiplicity of alternating SrTiO 3  layers and superconductive YBa 2  Cu 3  O 7  layers, each SrTiO 3  layer lying between two YBa 2  Cu 3  O 7  layers having a thickness of 20 to 30 nm, wherein said YBa 2  Cu 3  O 7  layers having thicknesses between 300 nm and 500 nm.